EVOLUTION: AGING

AGING

Some animals have a programmed life of growth, reproduction, and death; mayflies and salmon provide commonly known examples.  Others seem to continue indefinite slow growth after reaching reproductive maturity, crocodiles, some fish, and lobsters are examples.  Warm blooded vertebrates generally cease growth when sexually mature because the growth zones of bones have turned into bone, so growth is limited to adding bulk - something not needed to get through the seasons of reduced food supply now that modern food production and distribution has arrived.

How I Got Interested In The Physiology Of Aging

Along with the natural interest we have about our own life expectancy, I got a boost in my interest during my doctoral research comparing two species of isopods with greatly different life cycles.  The ecological factors and adaptive strategies were understandable in explaining the differences.

Less than ten years later I was involved in incorporating new information about the pogonophora in a textbook revision.  As mentioned in the previous post about Ocean Circulation, the abyssal ones had life cycles several orders of magnitude longer than terrestrial and shallow water organisms.  The most likely cause was an extreme deep-sea pressure affect not likely to be a factor for air-breathing organisms.

WHAT HAS HAPPENED

A lot has happened to about double the global average life expectancy of new-born babies in the last century.  Probably the greatest factors have been modern medicine, disease control, care of newborns, care of mothers.  Popular papers, magazines, and other sources of health information have been filled with information, much of it worth your time.  There does not appear to be a secret food, exercise, or supplement that will answer all your health needs  A balanced diet with portion control, reasonable activity, and physician recommended additions may be best in conjunction with.

No smoking
     avoids many cancers, emphysema, intolerant non-smokers, and stress on the heart

No, or very moderate alcoholic beverage drinking
     may help us avoid cirrhosis of the liver, deposition of excess abdominal fat, falls, accidents, and DUI citations, need to take vitamins and minerals to replace ones missed by less intake of fruits and vegetables

Moderation
     in activities and intake of sugars, protein, saturated fat, and total calories - all are better than too much or not enough

Social life, sleep, and mental activity
     yes, and you will probably be happier with your extra years

Pick your parents
      too late, it doesn't matter as much as our environment.  Superb genes will not help if we engage in unnecessary dangerous activity or ignore safety precautions.  But don't lament your poor genes, passing on good behavior can be a factor more important in survival of offspring.

STROKES AND HEART ATTACKS

and the mental deterioration we often think comes with old age may be minimized by healthy living and a love for one another.  We can be in great health with only minor accumulations of cholesterol induced deposits in blood vessels, but a sudden episode of extreme exertion could cause a few clumps in blood vessels to break free and plug blood flow to areas of the brain or heart,  If it hits an unused part of the brain it may be no problem.  If it is small enough it may be only a short term minor problem.  But don't take the chance if you have been long retired from vigorous activity.  Take a smaller shovel full of snow, or don't try to keep up with speedsters; pause and enjoy the beauty of the day, and thank God that there was a time when you could do that.

OTHER POSSIBLE AGING FACTORS

Amino acids are predominately bent in the "l" form and may over time be gradually converted to the "d" form giving rise to no, reduced, or different functionality.  The process is probably gradual but may speed up due to radiation or other factors.

Telomeres that terminate the chromosomes may be reduced each cell division and reduce cell replacement in aging organisms.

Accumulation of waste, or other, products in the cells may reduce or eliminate cell function.  Some organisms such as some bryozoans may dedicate scattered polyps of the colony as storage sites of waste.  We can't do that.  But our kidneys do their best to maintain chemical balance in the blood and eliminate many wastes.  However some pollutants and toxic substances accumulate over time and are poorly eliminated.

Fat soluble contaminants accumulate in body fat as well as the insulating layer of some nerve cell processes of nerves and the brain.  Metallic elements may be retained by combining with body proteins.  The cumulative effect of such things may be intensified by weight loss from disease or dieting.  Impairment of function of organisms can result from injury and scar tissue.

Evolution and grandparents

Multi-generational families are almost a thing of the past.  But they were important in our evolutionary history by
    providing child care for young during our long childhood
    transferring information prior to written and electronic storage and transfer
    source of knowledge and wisdom aiding survival
    being the weak prey picked off by predators so others escape
    monitoring and alerting

Considering genetic values that might not seem to have selective value until well after reproduction has ceased, such as factors that contribute to post-reproductive longevity, natural selection would still be effective.  The genes that may not become active until late in life would be expected to be favored by natural selection as they are almost certain to be more abundant in the reproducing offspring of the ones having genes favorable to aging.  It involves the same principle of group selection enabling sterile worker castes of insect to evolve features beneficial to the colony but only expressed in the sterile caste.

The rapid evolution of increased brain size in humans can probably be accounted for by the benefits of greater memory capacity.  Large brains of whales and elephants, although not disproportionately large as compared to humans, have a value for retention of migration histories and social behaviors beneficial to the groups survival.

Joseph Engemann    Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan      May 10, 2018